Fibromyalgia (FM) is a disorder characterized by widespread musculoskeletal pain and the presence of tender points. Other symptoms, including fatigue, sleep disturbance and neuropsychological complaints contribute significantly to the morbidity associated with FM. One of the most prominent complaints in patients with FM is impaired cognitive ability. However, there is limited data on actual cognitive function in FM. Nonetheless, these cognitive complaints interfere with work and disrupt the lives of FM patients. The data available from our current work on cognitive function in FM and from other research, point toward a deficit in executive control of cognitive processes, especially working memory. Two experiments are proposed that will investigate various aspects of executive control and task-switching ability. The design includes standard neuropsychological tests as well as techniques developed in cognitive psychology. The latter techniques involve manipulation of experimental factors such as delay between encoding and recall that affect particular cognitive processes, such as decay from memory. This type of design allows a detailed view of the specific cognitive processing mechanisms that are affected in FM. Because FM is associated with other symptoms that could impact cognitive function, two special control groups are included in the design in addition to healthy controls. A group of rheumatoid arthritis patients will provide a control for the attentional demands of managing chronic pain. A group of depressed patients will provide a control for depression in FM, since patients with FM frequently report more depressive symptoms than healthy controls. We hypothesize that FM is associated with cognitive dysfunction that cannot be explained solely on the basis of pain or depression. This research will lead to a better understanding of the characterization of cognitive dysfunction in FM, as well as the potential causes of this dysfunction. The emphasis on executive control processes is important because these are critical in many demanding work and life situations.